Apparatus for the manufacture of artificial silk



Nov. 25, 193C.

H. F. NiQGRET APBARATUS FOR THE MANUFACTURE OF ARTIFICIAL SILK Filed April 14, 1928 r so perature of condensation.

Patented Nev; 25,1930

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"l hi's inventionrelates to the manufacturef ofartifioial silk and niorejparticularlyato an apparatusfor dry spi nin'g cellulose derivatives. It especially adapted td the spin 5 ning ofasolutionof 'celluloseac'etate;

Considerable advantages have been obtained in the dry spinning of cellulose de rivatives by carrying out the-evaporation of the solvent or solvents, not in an atmo s-- phere containing but asmall proportion-of vapors of the solvent orsolvents but on the contrary in an atmosphere richly laden with these vapors. v

Also, it has been observed that the cross sectionof the filaments is. affected by causing the proportion of solvents in the :BVELPO'. rating atmosphere to vary,and in order to do this it has been proposed to use a method consisting in arranging a closed cirouitfor the evaporating atmosphere with direct condensation of the evaporated solvents and t0 fix the concentration of solvent vapors of the atmosphere in the cell by the selection of thetemperature of condensation. r I This method implied, therefore, an exit of the atmosphere at a certain point of the cell and at another point of the cell a readmittance of the same atmosphere partly freed from solvents in a desired proportion. ,I have now found that it is possible. to dispense withan external circuit for the evaporating atmosphere and according tothe present invention I perform the evaporation in an atmosphere richly laden with solvent vapors and obtain bya single large opening a gaseous exchange between the atmosphere of a heated cell where spinning is in process and the atmosphere ofha cooled condenser where the solvents condense, this condenser beingdirectly connected to the cell by the said aperture.

The atmosphere in the condenser is amixture of air and of solvent vapor, the composition of which is determined by the tem- The atmosphere of the cell also. is a mixture of air and of solvent vapor, the content of solvents being somewhat higher than that of'the atmosphereof the condenser. The difference between these two contents depends upon the conditions underw hichthe' convection cur i rents take placebetween these two" enclosures; j

, that is, uponj the dimensions@espectively of the cell andof thecondenser,upon'fthe q'iiani titjy of solvent evaporatedinjthe unit time; Y

most intense, er in other pointstr the, @611,

for example, at the end of the cell *opposed: to: the dies. I Several openin scom unicatin The filaments issue "from thetelrbyen yex trein'el'y small orifice, tether t 1 1ere&is"11o;a pireciable loss of solvent'vapors thisori- ,It ha b e eseeieained that ronieeai 100% of thesolventscontai ed nTthecollodiontobefspun can berecov red in these conditions, "this recover pbein eifeotedf inf an extremely" economical inanner by *direc 1 condensation; W

I describe hereaftenas an example which is not limitative,""anfapp aratiis worliin" in accordanc withthe preeerieinvemibn;

This description 'iss ecifietp afi apparatus; constitutinga spinning unit,butfit is evident that the spinning shed or n'ietier' may com prise-any number of'such-unit apparatus. 7 thei accompanying drawings; Figure 1, is a vertical-section ofv a'unit apparatus have:

tionto be spiiii is extrudedb bfthe usual K or known means. This verticaltube isheated by an external jacket 3. p p

A large apertureifl causes the cell to communicate with the eondenser 5, said con 55 w: and upon,,the difference of temperature diesitliat'loo denser being cooled by an external circulation of water or by any other means and provided with an outlet pipe terminating in a receiver 6 wherein the condensed solvent is collected. From the receiver 6 the condensed solvent may be caused to pass into the collector 7, the passage thereof being controlled by a valve 10.

At the lower portion of the cell is the opening 8 for the exit of the filaments. It is so disposed that there is practically no gaseous exchange with the atmosphere outside the cell. In this manner the working of the whole cell and condenser, is that of a practically closed space.

In Figure 2 there is illustrated an apparatus having two condensers, one disposed in the center of the cell and the other in the lower portion thereof, said condensers being identical in structure to that described above and illustrated in Figure 1. It is to be under stood that this figure (2) merely illustrates one modification wherein a plurality of condencers is utilized and that other positionings and/or number of condensers are possible and practical.

Under these conditions during normal spinning I have ascertained that, when spinning a. solution of cellulose acetate in acetone with a condenser maintained at a temperature of about 25 (3., the cell being heated at a temperature of C., 99% to 100% of the solvent contained in the solution to be spun is collected in the condenser 5 and recovered.

The atmosphere of the condenser comprises a mixture of air and acetone containing 700 grams per meter cube which corresponds to saturation at the temperature of 25 C.

The atmosphere of the cell comprises a mixture of air and acetone varying between 700 grams and 1,000 grams per meter cube. The thread issues from the cell substantially dry.

At the instant of starting and during a .short interval of time the apparatus is exhausted so as to free it from the excess of air it contains with respect to the quantity of air which must finally remain in the system. This exhaustion takes place, for instance. by means of a neck 9 which may be if desired connected to a recovery installation which will be naturally of very small capacity.

In. this example it has been. stated that the condenser is cooled by a circulation of outside water or by any other means. Satisfactory cooling may be obtained by utilizing the atmospheric air of the spinning room. When this latter method is employed, it is desirable that the condenser be of such shape or form and/or provided with other means to augment its cooling surface such as, for example, fins or small wings. 7

Having now particularly described and ascertained the nature of my saidinvention;

tions of cellulose derivatives in volatile solvents comprising a closed cell, means for heatmg said cell, a plurality 0t condensers each condenser being directly connected to the cell by a single large aperture, and means for cooling said condensers.

In testimony whereof, I have affixed my signature to this specification.

HENRI FRANQOIS NIOGRET. 

